SpiritedAway is a menubar gadget that keeps an eye on the windows that are open on your desktop. After a predetermined time, SpiritedAway will hide any windows that are not currently front and center.

When it's first launched, you are presented with a slider where you choose the delay before hiding windows.

After that, SpiritedAway quietly goes about its business—de-cluttering your desktop. If you're working on a project and you decide that you don't want a particular item hidden, you can choose to exclude that item via the menu.

As always, any hidden item can be called up via the Dock, or Command—Tab, or via whatever shortcut you currently use to call up that particular application.

If you're in the habit of hiding items, I recommend setting the Dock to show their icons as transparent; this can be setup via TinkerTool.